This application is a 371 of PCT/FR99/00586 filed Mar. 16, 1999.
The present invention relates to stable emulsions comprising a continuous phase formed from a solution of an elastomer in an organic solvent and a dispersed phase, in the form of droplets with a diameter greater than or equal to 10 xcexcm; said droplets comprise an active chemical substance in a solvent which is immiscible with the elastomer solution and are capable of being converted into elastomeric films.
The present invention also relates to the process for preparing said emulsions, as well as to elastomeric films containing them: said emulsions can give, after evaporation of the solvent for the elastomer, an elastic film containing stable droplets of liquid, with a diameter of greater than or equal to 10 xcexcm.
International patent application WO 95/17453 in the name of the Applicant describes the preparation of a two-phase solid material containing a dispersion of liquid droplets of an active chemical substance, which are stabilized by means of a block or grafted copolymer comprising at least a number of sequences polyB which are compatible with said droplets and a number of polyA sequences, which are immiscible with these droplets, in an elastomer. The droplets generally have a diameter of less than 10 xcexcm. Under these conditions, the block or grafted copolymer effectively stabilizes the emulsion, which is thus distributed homogeneously in said film.
That international patent application WO 95/17453 also describes the process for preparing said elastomeric material; this process essentially comprises two steps:
(1) the preparation of an emulsion which comprises:
the preparation of a phase A by dissolving the elastomer in an organic solvent a (phase A: solution of elastomer in the organic solvent a)
the preparation of a phase B, by mixing an active chemical substance in an organic solvent b which is immiscible with phase A (phase B: solution or dispersion of active substance in an organic solvent b which is immiscible with the phase A)
the addition to phase A or phase B, in proportions of from 0.1 to 50%, preferably from 0.1 to 25%, of a block or grafted copolymer comprising at least a number of polyA sequences, which are miscible with the phase A, and a number of polyB sequences, which are miscible with the phase B, as defined above
the dispersion of phase B in phase A to give an emulsion in which phase A constitutes the continuous phase and phase B constitutes the dispersed phase, as represented in FIG. 1, and
(2) evaporation of the organic solvent a to give an elastomeric film containing, in the form of a stable dispersion, droplets of solvent b generally less than 10 xcexcm in diameter, loaded with active chemical substance.
Continuing its research, the Applicant became interested more particularly in improving the stability of emulsions B in A in step (1), in particular those with droplets at least equal to 10 xcexcm in diameter and preferably between 10 and 50 xcexcm in diameter.
The various elastomeric materials usually used in the medical or paramedical field (in particular hygiene) can be modified so as to be combined with active chemical substances, having a protective effect, during the use of this [sic] materials (gloves, fingerstalls, condoms, strips and various dressings). Specifically, both in the case of examination or surgery or in odontology, and for protection against pathogenic agents such as, for example, bacteria, viruses and fungal spores, a rupture or sometimes even simply the pores or a crack in the elastomeric membrane can result in the wearer of said material becoming contaminated by being pricked with syringes, suture needles, trocars, bone splinters, etc.
Now, if the droplets containing the active chemical substance, which may be released in the event of rupture of the protective elastomeric material, do not release a sufficient amount of active substance, the protective effect will not be sufficient.
Moreover, if the diameter of the droplets is increased, so as to allow the release of a sufficient effective amount of active substance to rapidly neutralize the pathogenic agent which may thus have been accidentally introduced into the wearer, the problem of the stability of the emulsion may become crucial.
According to the literature (P. Becher, Emulsion: Theory and Practice, ACS Monogr., 162, 1965), an emulsion can be defined as xe2x80x9ca heterogeneous system consisting of at least one immiscible liquid intimately dispersed in another in the form of dropletsxe2x80x9d. These systems generally contain one or more surfactants, like the block or grafted copolymers described in international patent application WO 95/17453. In this case, the particles are subjected to Van der Waals attraction forces and electrostatic or steric repulsion forces associated with the presence of copolymer, as well as to gravitational forces, if the densities of the phases present are different.
The equilibrium between the forces of attraction and repulsion is the origin of stabilization or destabilization of the emulsions.
Two main destabilization mechanisms should be envisaged for these systems:
flocculation, which is reflected by an aggregation of particles in the form of clusters, and
coalescence, which is the result of thinning of the liquid film separating the particles and is reflected by fusion of the particles to form a single particle of larger size.
The block or grafted copolymers as described in international patent application WO 95/17453 are particularly suitable for stabilizing emulsions comprising droplets less than or equal to 10 xcexcm in diameter, by reducing the phenomena of coalescence and/or flocculation.
The Applicant has now found that to stabilize droplets of a phase B (containing an active chemical substance x and a solvent b) with a diameter xe2x89xa710 xcexcm, dispersed in an organic phase A (elastomer+solvent a), said block or grafted copolymers must be used as a mixture with other compounds of particle-stabilizing type, in order to effectively obtain stabilization of the emulsion.
The Applicant has also found that, when the emulsion comprises certain chemical substances x which have surfactant properties, it is possible to reduce the content of block or grafted copolymer, or even to dispense with it altogether. In such a case, said chemical substance included in phase B and combined with the particulate stabilizer also makes it possible to obtain a stable emulsion.
A subject of the present invention is a stable emulsion of at least one chemical substance x in an elastomer solution, which can be used for the preparation of an elastomeric film, comprising (1) a phase A comprising an elastomer dissolved in an apolar or relatively nonpolar organic solvent a, in which is dispersed (2) a phase B comprising at least said chemical substance x dissolved or dispersed in a polar solvent b, which is immiscible with phase A, and (3) at least one dispersing agent selected from the group consisting of block or grafted copolymers, this emulsion being characterized:
in that the droplets of dispersed phase B have a diameter xe2x89xa710 xcexcm,
in that said emulsion comprises, for the stabilization of said dispersed phase B, besides at least one block or grafted copolymer (also referred to as dispersing copolymer) comprising polyA sequences which are compatible with phase A and polyB sequences which are compatible with phase B, at least one particulate stabilizer selected from the group consisting of solid organic compounds of between 30 nm and 10 xcexcm in size or solid inorganic compounds of between 5 nm and 10 xcexcm in size, of any geometry (sphere, parallelepiped, finely divided solid, etc.), whose surface is organophilic in nature,
in that the mass fraction xcfx86B of dispersed phase (phase B) in the emulsion, expressed by:       φ    B    =            m      B                      m        B            +              m        A            +              m        elastomer            
xe2x80x83is between 0.01 and 0.2,
with mB=mass of phase B (solvent b+active chemical substance x)
mA=mass of solvent a
melastomer=mass of the elastomer dissolved in a;
in that the mass fraction of the block or grafted copolymer (dispersing copolymer, DC), xcfx86DC, expressed relative to the dispersed phase B, i.e.:       φ    DC    =            m              D        ⁢                  xe2x80x83                ⁢        C                            m                  D          ⁢                      xe2x80x83                    ⁢          C                    +              m        B            
xe2x80x83is between 0.001 and 0.3, preferably between 0.01 and 0.2,
with mB=mass of phase B (solvent b+active chemical substance x)
mDC=mass of dispersing copolymer; and
in that the mass fraction of particulate stabilizer (PS), xcfx86PS, formed in situ or added as an adjuvant, expressed relative to the dispersed phase B, i.e.:       φ    PS    =            m      PS                      m        PS            +              m        B            
xe2x80x83is between 0.001 and 0.5,
with mPS=mass of particulate stabilizer
mB=mass of phase B (solvent b+active chemical substance x).
For reasons of convenience, the proportions of the various constituents of the emulsion are expressed in mass fractions rather than in volume fractions.
Preferably, said mass fraction of the block or grafted copolymer, xcfx86DC, is between 0.001 and 0.2, preferably between 0.01 and 0.1.
The expression xe2x80x9cparticulate stabilizer whose surface is organophilic in naturexe2x80x9d means a solid organic compound, in particular of polymeric type, or a solid inorganic compound, finely divided and dispersible in the continuous phase (phase A); the surface nature can be modified by means of a surface-treating agent, to make said particulate stabilizer organophilic.
In such emulsions, the block or grafted copolymer denoted by dispersing copolymer serves essentially to facilitate the dispersion of one liquid in the other when the emulsion is prepared, by lowering the interface tension between phase A and phase B, and only partially to stabilize the droplets since this stabilization is essentially provided by the particulate stabilizer.
Surprisingly, the combination of a dispersing copolymer and a particulate stabilizer makes it possible to stabilize an emulsion comprising droplets of diameter xe2x89xa710 xcexcm. Specifically, in such a case, the particulate stabilizer alone has no dispersing effect and does not allow the emulsion to be prepared; similarly, the dispersing copolymer alone does not stabilize the emulsion sufficiently.
A synoptic scheme representing a droplet of emulsion stabilized by means of a mixture of dispersing copolymer and a particulate stabilizer is represented in FIG. 2.
In accordance with the invention, when the particulate stabilizer is of organic nature, it is essentially of polymeric type and is selected from the group consisting of organophilic block or grafted copolymers, identical to or different than those used as dispersing copolymers, which are capable of forming structures with a diameter of greater than 30 nm and cellulose derivatives such as microcellulose, starch or certain finely divided polymers; in this case, said particulate stabilizer is:
either naturally organophilic (block or grafted copolymers), on account of the presence of a fleece of polyA sequences at its surface; it can then be:
formed in situ in the solvent a for phase A; in this case, it is preferably identical to the dispersing copolymer and is selected from block copolymers capable of forming, in addition to xe2x80x9cstandardxe2x80x9d micelles, other set structures, greater than 30 nm in size, such as, for example, structures of xe2x80x9ctilexe2x80x9d type (detailed in Example 1) or any other copolymer aggregate of less well defined geometry. It is all these combined and set structures which can behave like a particulate stabilizer. Preferably, such a particulate stabilizer is selected from the group consisting of copolymers containing a crystallizable polyB sequence, such as, for example; polyoxyethylene, poly(ethylene), polyamide or polyester such as poly(caprolactone), given that the polyA sequence must be soluble in phase A of the emulsion, or
added in the form of combined and set structures greater than 30 nm in size, formed by a block copolymer and isolated beforehand from other small structures such as micelles. In this case, the particulate stabilizer can optionally be of a different chemical nature than that of the dispersing copolymer, but is selected from the particulate stabilizers as defined above.
or made organophilic and added as an adjuvant before, during or after formation of the emulsion; it is selected from cellulose derivatives such as microcellulose, starch or certain finely divided polymers;
xe2x80x83it is made organophilic by treatment of its surface with a surface-treating agent capable of making it organophilic and thus dispersible in phase A of the emulsion, and of giving it steric-mediated stabilizing properties; the mass fraction of the surface-treating agent used to make the surface of the particles organophilic, i.e. xcfx86STA, expressed relative to the particulate stabilizer, i.e.:       φ    STA    =            m      STA                      m        PS            +              m        STA            
xe2x80x83is between 0.001 and 0.5,
with mSTA=mass of the surface-treating agent
mPS=mass of particulate stabilizer.
Preferably, said mass fraction of the surface-treating agent, xcfx86STA, is between 0.001 and 0.1.
Also in accordance with the invention, when the particulate stabilizer is of inorganic type, this stabilizer is chosen from the group which comprises clays, silicas, talc, kaolin and derivatives of these products and is surface-treated with a surface-treating agent which is capable of making it organophilic and thus dispersible in the continuous phase (phase A) of the emulsion, and of giving it steric-mediated stabilizing properties, and is added, as an adjuvant, to phase A containing the solution of elastomer in solvent a and the dispersing copolymer; the mass fraction of surface-treating agent relative to the particulate stabilizer for the emulsion is between 0.001 and 0.5, as specified above.
Preferably, said mass fraction of the surface-treating agent, xcfx86STA, is between 0.001 and 0.1.
As a variant, the inorganic particulate stabilizer can be chosen from commercially available xe2x80x9corganophilicxe2x80x9d products, such as, for example, certain organophilic silicas or clays (Bentone 38, Bentone SD-1, Rheox Inc., etc.), and consequently does not require any additional surface-treating agent. These various possibilities-are summarized in FIG. 4.
According to one advantageous embodiment of said emulsion, it comprises several particulate stabilizers, such as, for example, the combination of a particulate stabilizer formed in situ during the dissolution of the dispersing copolymer with a second particulate stabilizer in the form of an adjuvant.
According to another advantageous embodiment of said emulsion, the dispersing block copolymer is selected from diblock copolymers of polyA-block-polyB type, triblock copolymers of polyB-block-polyA-block-polyB (BAB) type, of polyA-block-polyB-block-polyA (ABA) type, of polyA-block-polyB-block-polyC (ABC) type or of polyA-block-polyC-block-polyB (ACB) type, or more generally from multiblock compounds containing polyA, polyB and polyC sequences and the copolymer of the grafted dispersing type is selected from compounds of polyA-grafted-polyB type, polyB-grafted-polyA type, polyA-grafted-polyB and polyC type or polyC-grafted-polyA and polyB type.
The proportions of polyA sequence, expressed by mass relative to the sum of the polyA+polyB sequences, are between 10 and 90%, and the proportions of polyB sequences are between 90 and 10%, and the mass proportions of polyC sequences are between 0 and 50% relative to all of the sequences.
The molar masses of the polyA, polyB and polyC sequences are between 1000 and 500,000 daltons.
In accordance with the invention, the polyA sequences, which are compatible with the apolar or relatively nonpolar solvent a, are selected from the group consisting of polydienes, polyolefins, polyethers and silicones, such as polyisoprene, polybutadiene, polyisobutene, hydrogenated polybutadiene or hydrogenated polyisoprene, poly(4-tert-butylstyrene), polyoxypropylene, polyoxybutylene, polydimethylsiloxane, poly(2-ethylhexyl methacrylate) or poly(lauryl methacrylate), which are miscible with a solution of elastomer in a solvent a, the polyB sequences, which are compatible with the solvent b, are selected from the group consisting of polyoxyethylene, polyvinylpyrrolidone, polyacrylic acids, poly(vinyl alcohol) and quaternized poly(vinylpyridine).
The polyC sequences can be chosen from the group which comprises polymers which may be either compatible with the solvent a or the solvent b, or incompatible with the solvents a and b. The polyC sequence is chosen, in a non-limiting manner, from the group formed by acrylic or vinyl polymers such as poly(methyl methacrylate) or polystyrene.
According to another advantageous embodiment of said emulsion, the surface-treating agent, which is capable of making the particulate stabilizer organophilic, is selected from the group consisting of block or grafted copolymers containing at least one polyAxe2x80x2 sequence which is soluble in the solvent a, and a polyBxe2x80x2 sequence capable of being adsorbed onto or binding to the surface of the particulate stabilizer, said polyAxe2x80x2 and polyBxe2x80x2 sequences being identical to or different than the polyA and polyB sequences and functionalized oligomers of polyAxe2x80x2-F type, in which F is a chemical function capable of being adsorbed onto the particulate stabilizer.
In accordance with the invention,, the polyAxe2x80x2 sequences are chosen from polymers which are soluble in the apolar or relatively nonpolar solvent a, such as, for example, from the group which comprises polydienes, polyolefins, polyethers and silicones, such as polyisoprene, polybutadiene, polyisobutene, hydrogenated polybutadiene or hydrogenated polyisoprene, poly(4-tert-butylstyrene), polyoxypropylene, polyoxybutylene, polydimethylsiloxane, poly(2-ethylhexyl methacrylate) or poly(lauryl methacrylate), which are miscible with a solution of elastomer in a solvent a, and the polyBxe2x80x2 sequences are chosen from polymers capable of being adsorbed onto the surface of the particulate stabilizer, and is chosen from the group which comprises polyoxyethylene, polyvinylpyrrolidone, polyacrylic acids, poly(vinyl alcohol) and quaternized or nonquaternized poly(vinylpyridine).
According to another advantageous embodiment of the emulsion, the proportions of polyAxe2x80x2 sequence, expressed by mass relative to the sum of the polyAxe2x80x2+polyBxe2x80x2 sequences, are between 10 and 90%, preferably between 20 and 80%, and the proportions of polyBxe2x80x2 sequences are between 90 and 10%.
According to yet another advantageous embodiment of said emulsion, the molar masses of the polyAxe2x80x2 and polyBxe2x80x2 sequences are between 150 and 200,000 daltons.
According to another advantageous embodiment of said emulsion, F is selected from the group consisting of acid, amine or alcohol functions and groups capable of reacting chemically with the surface of the particulate stabilizer, such as, for example, epoxy, isocyanate or aziridine groups.
Such emulsions of an active chemical substance x in an elastomer solution comprise droplets which have a diameter greater than or equal to 10 xcexcm and very good stability imparted jointly by said block or grafted copolymer and by said particulate stabilizer made organophilic by means of a surface-treating agent as defined above.
The stability of said emulsions can be evaluated by detecting the phenomena of coalescence and flocculation, as well as by monitoring the diameter of the droplets over time.
The elastomer, the solvent a, the active chemical substance x and the solvent b are, in particular, those described in international patent application WO 95/17453.
For example:
the elastomer is selected, in a non-limiting manner, from the group consisting of polybutadiene, polyisoprene, polychloroprene, SBR (styrene butadiene rubber) copolymers, NBR (nitrile butadiene rubber) copolymers, SBS (styrene butadiene styrene) copolymers, SIS (styrene isoprene styrene) copolymers, SEBS (styrene ethylene-co-butylene styrene) copolymers, alone or as a mixture with one or more plasticizers or flexibilizing agents.
the apolar or relatively nonpolar solvent a is chosen in particular from aliphatic, aromatic and alicyclic hydrocarbons, for example methylcyclohexane, toluene, heptane or a mixture thereof.
the active chemical substance x is selected from compounds capable of bringing about virtually instantaneous denaturing of proteins by means of simple contact, either by chemical reaction or by a physicochemical effect such as a modification of the surface tension. This family of compounds comprises, inter alia, biocides, such as quaternary ammoniums, preferably dimethyldidecylammonium chloride, biguanides, phthalaldehyde, phenolic or benzylic derivatives, formaldehyde, nonionic surfactants comprising at least one polyoxyethylene sequence, hexamidine, iodine-containing polyvinylpyrrolidone compounds, nonionic surfactants with virucide activity, and sodium and potassium dichromates and hypochlorites, used alone or as a mixture.
the solvent b is immiscible with the solvent a as defined above. b is selected, for example, from polyols, and preferably glycerol, ethylene glycol and polyethylene glycols which are liquid at room temperature and have a molar mass of between 62 (ethylene glycol) and 750 daltons (PEG-750), but can be any other compound which is immiscible with the solvent a, such as, for example, water, dimethyl sulfoxide, formamide or ethanolamine or mixtures of such solvents.
Preferably, the mass fraction of the active chemical substance x, i.e. xcfx86x, in the emulsion described above is expressed by       φ    x    =                    m        x                              m          x                +                  m          b                      =                  m        x                    m        B            
and is between 0.01 and 0.7, preferably between 0.1 and 0.4,
with mx=mass of active chemical substance x
mb=mass of solvent b
mB=mass of dispersed phase B.
As a variant, if the active chemical substance x has surfactant properties, i.e. if it allows the interface tension between phase A and phase B to be reduced, which is the case in particular for quaternary ammoniums, nonionic surfactants comprising at least one polyoxyethylene sequence and nonionic surfactants with virucide activity, this active chemical substance x can act as a dispersant. The result of this is that, under these conditions, it is possible to reduce the content of block or grafted copolymer in the emulsion described above, or even to dispense with it altogether, thus simplifying the formulation of the emulsion according to the invention while still providing suitable stabilization of the droplets with a diameter xe2x89xa710 xcexcm.
A subject of the present invention is thus also a stable emulsion of at least one chemical substance x in an elastomer solution, which can be used, to prepare an elastomeric film, comprising (1) a phase A comprising an elastomer dissolved in an apolar or relatively nonpolar organic solvent a, in which is dispersed (2) a phase B comprising at least said chemical substance x, dissolved or dispersed in a polar solvent b, which is immiscible with the phase A, this emulsion being characterized:
in that the droplets of dispersed phase B have a diameter xe2x89xa710 xcexcm,
in that said emulsion comprises, to stabilize said dispersed phase B, (1) at least one chemical substance x, this substance having surfactant properties and acting as a dispersant, said chemical substance x being selected from the group consisting of quaternary ammoniums, nonionic surfactants comprising at least one polyoxyethylene sequence and nonionic surfactants with virucide activity, and (2) at least one particulate stabilizer as defined above, preferably formed from a block or grafted copolymer,
in that the mass fraction xcfx86B of the dispersed phase (phase B) in the emulsion, expressed by:       φ    B    =            m      B                      m        B            +              m        A            +              m        elastomer            
xe2x80x83is between 0.01 and 0.2,
with mB=mass of phase B (solvent b+active chemical substance x)
mA=mass of solvent a
melastomer=mass of the elastomer dissolved in a;
in that the mass fraction of the active chemical substance x, i.e. xcfx86x, expressed by       φ    x    =                    m        x                              m          x                +                  m          b                      =                  m        x                    m        B            
xe2x80x83is between 0.01 and 0.7, preferably between 0.1 and 0.4,
with mx=mass of active chemical substance x
mb=mass of solvent b
mB=mass of dispersed phase B,
in that the mass fraction of particulate stabilizer (PS), xcfx86PS, formed in situ or added as an adjuvant, expressed relative to the dispersed phase B:       φ    PS    =            m      PS                      m        PS            +              m        B            
xe2x80x83is between 0.001 and 0.5,
with mPS=mass of particulate stabilizer
mB=mass of phase B.
Advantageously, said elastomer, said solvent a, said solvent b and said particulate stabilizer are as defined above in the context of the emulsions comprising a dispersing agent selected from the group consisting of block or grafted copolymers.
Surprisingly, the combination of the active chemical substance x with surfactant properties and the particulate stabilizer(s) preferably when these are block or grafted copolymers as defined above, makes it possible to stabilize an emulsion comprising droplets with a diameter xe2x89xa710 xcexcm.
A subject of the invention is also a process for preparing said stable emulsion:
I. When the particulate stabilizer is added before the formation of the emulsion, this formation is carried out as follows:
the preparation of a phase A by dissolving the elastomer in an organic solvent a (phase A: solution of elastomer in the organic solvent a),
the preparation of a phase B, by mixing an active chemical substance x in an organic solvent b which is immiscible with phase A (phase B: solution or dispersion of active substance in an organic solvent b which is immiscible with phase A),
the addition to phase A or phase B, in proportions as defined above, of a block or grafted copolymer serving essentially as a dispersing copolymer; however, if this copolymer is capable of forming in situ, in phase A, in addition to a standard organization of micellar type, other combined and set structures with a diameter of greater than 30 nm, which can act as particulate stabilizer, the latter no longer needs to be added in a subsequent step; when said copolymer comprises a crystallizable polyB sequence, it is effectively capable of forming in situ, in phase A, in addition to a standard organization of micellar type, other combined and set structures which can act as particulate stabilizer. In the opposite case, the addition to phase A of the mass fraction of the particulate stabilizer, as defined above, is carried out in a second stage, in the form of an adjuvant. This solid organic or inorganic compound is organophilic and thus, if necessary, is pretreated with a surface-treating agent, as specified above, and
the dispersion of phase B in phase A, to obtain an emulsion in which phase A constitutes the continuous phase and phase B constitutes the dispersed phase.
When the active chemical substance x acts as a dispersing agent, the process for preparing the emulsion is carried out as follows, when the particulate stabilizer is added before formation of the emulsion:
the preparation of a phase A by dissolving the elastomer in an organic solvent a (phase A: solution of elastomer in the organic solvent a),
the preparation of a phase B, by mixing the active chemical substance x of surfactant nature in an organic solvent b which is immiscible with phase A (phase B: solution or dispersion of active substance in an organic solvent b which is immiscible with phase A),
the addition to phase A or phase B, in proportions as defined above, of an organophilic particulate stabilizer or one which has been made organophilic, preferably formed from a block or grafted copolymer,
the dispersion of phase B in phase A to obtain an emulsion in which phase A constitutes the continuous phase and phase B constitutes the dispersed phase.
II. When the particulate stabilizer is added after formation of the emulsion, this formation is carried out as follows:
the preparation of a phase A by dissolving the elastomer in an organic solvent a (phase A: solution of elastomer in the organic solvent a),
the preparation of a phase B, by mixing an active chemical substance x in an organic solvent b which is immiscible with phase A (phase B: solution or dispersion of active substance in an organic solvent b which is immiscible with phase A),
the addition to phase A or phase B, in proportions as defined above, of a block or grafted copolymer serving essentially as a dispersing copolymer,
the dispersion of phase B in phase A to obtain an emulsion in which phase A constitutes the continuous phase and phase B constitutes the dispersed phase,
the addition, with stirring, of the organophilic particulate stabilizer as defined above.
When the active chemical substance x acts as a dispersing agent, the process for preparing the emulsion is carried out as follows, when the particulate stabilizer is added before or after formation of the emulsion:
the preparation of a phase A by dissolving the elastomer in an organic solvent a (phase A: solution of elastomer in the organic solvent a),
the preparation of a phase B, by mixing the active chemical substance x of surfactant nature in an organic solvent b which is immiscible with phase A (phase B: solution or dispersion of active substance in an organic solvent b which is immiscible with phase A),
the dispersion of phase B in phase A to obtain an emulsion in which phase A constitutes the continuous phase and phase B constitutes the dispersed phase, and the simultaneous or non-simultaneous addition, with stirring, of the particulate stabilizer which is organophilic or which has been made organophilic, preferably formed from a block or grafted copolymer.
As a variant, the particulate stabilizer is added before formation of the emulsion, i.e. when phase B is dispersed in phase A.
As a variant, the particulate stabilizer can be made organophilic directly by the copolymer used to disperse the emulsion.
These various alternatives are summarized in FIG. 5.
A subject of the present invention is also an elastomeric film, characterized in that it is obtained by evaporating the solvent a from an emulsion as defined above.
Such an elastomeric film, which can advantageously serve as a protective support, comprises stable droplets of a solvent b which is immiscible with the elastomer, loaded with at least one active substance x, these droplets having a diameter xe2x89xa710 xcexcm and being uniformly distributed throughout the elastomeric material.
In accordance with the invention, the combination of at least one block or grafted copolymer and at least one particulate stabilizer makes it possible to obtain the stability of the emulsion both in the presence of the solvent a and during the evaporation of said solvent a, i.e. during the formation of the film, which, itself, is stable and has optimum mechanical properties.
The subject of the present invention is also a process for preparing said elastomeric film, characterized in that it comprises:
(a) the preparation of an emulsion as defined above, and
(b) the evaporation of the organic solvent a to obtain an elastomeric film containing, in the form of a stable dispersion, droplets of solvent b, loaded with active chemical substance x, with a diameter xe2x89xa710 xcexcm.
A subject of the present invention is also the various uses of the elastomeric film according to the invention, more particularly in the medical and paramedical fields: gloves, fingerstalls, condoms or dressings comprising an elastomeric film in accordance with the invention.